1. Field of the Invention
The present invention relates to the field of liquid crystal displaying technology, and in particular to a backlight module and a liquid crystal display device.
2. The Related Arts
A conventional liquid crystal display device often uses a white light-emitting diode (LED) as a backlight source, which, when properly arranged in combination with a light guide plate and an optic film, could achieve desired backlighting for liquid crystal. With the increasing demands of people for high color gamut, high color saturation, and energy saving, the solutions that are conventionally adopted to achieve white light source, high color gamut, and high color saturation include: using a violet LED in combination with red, green, and blue phosphors; using a blue LED in combination with red and green phosphors; and using a blue LED together with a green LED and a red LED. All these solutions help increase color gamut, but they are difficult to put into practice and costs are high.
The quantum dot (QD) technique is a technique related to a structure of a semiconductor nanometer material that confines electrons in a predetermined range and is composed of extremely small crystals of chemical compounds having a size ranging 1-100 nm. In the QD technique, crystals of different sizes can be used to control light wavelength in order to achieve precise control of light color. Thus, QD materials are used in backlight modules and a light source of a high frequency spectrum (such as a blue LED) is used to replace the conventionally used white LED light source. Being irradiated by lights of high frequencies, the QDs can be excited to emit lights of different wavelengths. Adjusting the size of the QD material would allow for adjustment of the color of the combined light so as to satisfy the demand for backlighting of high color gamut liquid crystal display modules.
FIG. 1 shows a known backlight module that uses a quantum dot phosphor film. Referring to FIG. 1, a blue light-emitting diode (LED) 11 is arranged at a light incidence side surface of a light guide plate 12 and a quantum dot phosphor film 13 is arranged on a light exit surface of the light guide plate 12, wherein light emitting from the blue LED 11 is converted by the light guide plate 12 into planar light and is projected from the light exit surface of the light guide plate 12 to pass through the quantum dot phosphor film 13, where the blue light is converted into backlighting required for a liquid crystal display device. However, for a large-sized liquid crystal display device, the quantum dot phosphor film 13 must be formed as a large area and this requires an increased amount of quantum dot material. Further, coating of the quantum dot phosphor layer is subjected to severe requirement for uniformity and this leads to a high cost. Further, in the use of the quantum dot phosphor film 13, if the configuration of the optic film or the model number of the optic film is different, the light, which is subjected to improvement made by the optic film, after transmitting through the liquid crystal display panel, shows great variations in respect of color and brightness and thus, during the use of the quantum dot phosphor film 13, it is generally not allowed to change the optic film configuration, the optic film supplier, or the optic film model number. This imposes limitations to the flexibility and universality of use of the quantum dot phosphor optic film.
FIG. 2 shows another known backlight module that uses a quantum dot phosphor film. Referring to FIG. 2, a blue LED 21 is arranged at a light incidence side surface of a light guide plate 22 and a quantum dot phosphor is packaged in a glass tube to form a quantum dot phosphor contained glass tube 23, wherein the quantum dot phosphor contained glass tube 23 is disposed between the blue LED 21 and the light incidence side surface of the light guide plate 12. The blue LED 11 emits blue light that passes though the quantum dot phosphor contained glass tube 23 to irradiate the light incidence side surface of the light guide plate 12. However, adopting this solution requires a complicated manufacture of the quantum dot phosphor contained glass tube 23 and the cost is high. Further, the quantum dot phosphor contained glass tube 23 is susceptible to breaking.